Antenna



April 11, 1939. HQPETERS N 2,153,589

ANTENNA Filed May 19, 1936 RmEcmR CONDUCTOR INVENTOR HAROLD O. ETERSON/IANC ATTO RNEY Patented Apr. 11, 1939 PATENT OFFICE ANTENNA Harold 0.Peterson, Riverhead, N. Y., asalgnor to Radio Corporation of America, acorporation of Delaware Application May 19, 1936, Serial No. 80,498

8 Claims.

The present invention relates to antennas, and particularly to anantenna system for radiating horizontally polarized waves substantiallyequally in all directions in the horizontal plane.

The vertical antennas commonly used at transmitters for broadcastingpurposes have the property of radiating vertically polarized wavessubstantially equally in all directions along the horizontal plane. Itis in some cases found desirable to radiate energy which is horizontallypolarized, since a horizontally disposed receiving antenna will in manycases be less susceptible to local interference than one oriented forthe reception of vertically polarized waves. It is, however, notpossible to broadcast horizontally polarized waves in all directionswith the horizontal type of doublet antenna commonly used, inasmuch asthese have a directive characteristic whereby they radiate very littleenergy in a direction parallel to the length of the doublet. The presentinvention provides an emcient antenna system which radiates horizontallypolarized waves substantially equally in all directions.

Referring to the drawing, Figs. 1, 2, 8. 4, 5 and 6 illustrate,diagrammatically, transmitting antennas in accordance with theinvention, for producing radiation of horizontal polarization with equalefllciency in all directions. Figs. 4a and 4b are given to illustratethe distribution of current amplitude on the two halves of the system ofFig. 4 at any instant.

Fig. 1 shows an antenna comprising a conductor I arranged in the form ofa circle in the horizontal plane and having a diameter equal to where Ais the wavelength. In other words, the diameter shown in Fig. 1 is suchthat the circumference is approximately two wavelengths long. If thecircumference is chosen to be an even integer number of wavelengthslong, such circumference must be used that will produce a diameter closeenough to an odd number of half wavelengths, so as to producesubstantially equal radiation in the horizontal plane. Similarly, if thecircumference is chosen to be an odd integer number of wavelengths long,such circumference must be used that will produce a diameter closeenough to an even number of half wavelengths to achieve the same result.In other words, suitable lengths must be chosen to satisfy the abovewill vary therefrom, although substantially obeying the laws set forthabove. This relationship is required to be such that the radiationfields from current elements in opposite sides of the circumference addup in phase at a distance. In the case of Fig. 1, this condition issatisfied for radiation in directions inclined 38 from the plane of theloop. In other words, optimum radiation for the system of Fig. 1 is atan angle of 38 from the plane of the loop. It should be understood,however, that although optimum radiation is at an angle to the plane ofthe loop in the system of Fig. 1, that the waves are radiatedsubstantially equally in all directions in the plane of the loop. Foroptimum radiation in the plane of the loop it would be necessary tomodify the dimensions of Fig. 1 so that the diameter is 0.88). 1 Thisvalue is derived as follows for optim radiation in the plane of theloop: Let

360.1r.R o 360.2.R A 180 wherein the term through two diametricallyopposite points in the loop.

The term represents the phase delay in degrees, of the space wave intraveling across the diameter of the loop.

This equation reduces to R=.44 The energy from the transmitter T, hereshown conventionally, is fed through a radiationless type oftransmission line TL into this circular shaped conductor at one end, andthe other end of the conductor is damped by means of surge resistance Rso that flow of energy along the conductor is in one direction only, andconsequently no standing waves exist on the conductor. The current wavesin the conductor travel in the direction indicated by the arrow. Theeffect of this travelling current wave on the wire is to produceinstantaneously maximum radiation in certain directions and minimumradiations in other directions; However, the direction of maximum andminimum radiation changes as the current wave progresses around thewire, resulting in substantially equal radiation of energy in alldirections along the horizontal plane. The broken lines around theantenna I indicates the current amplitude distribution at a giveninstant.

Fig. 2 illustrates a modification of this type of radiator in which acylindrical reflector 2 is placed inside of the circle and spaced fromthe conductor by a suitable amount sufficient to give reflection ofproper phase. Fonthis condition, the antenna will be spacedapproximately onequarter wavelength from the reflector. Reflector 2 ispreferably made of metal, although it may be made of a substance whosedielectric constant is considerably greater than that of air.

Fig. 3 shows, in cross section, a modification of this reflector whereina circular antenna conductor 3 is placed between two annular reflectors4, 4' which face one another and are designed, in the manner shown, togive concentration of energy in the vertical plane. This system of thisfigure, as well as that of Fig. 2, may be energized in the same manneras that of Fig. 1 so as to preclude the formation of standing waves.

Fig. 4 shows a system utilizing two parallel circles of conductors 5, 5'fed from a symmetrical and closely spaced transmission line T11 andspaced apart by approximately one-half the length of the communicationwave. The ends of transmission line TL are normally in phase opposition.Since both of the parallel conductors extend in the same drection, it istherefore necessary to interpose a one-half wave section of line S inseries with one side of the transmission line so that the currents inthe two circular antennas will be cophasal. Another one-half wavesection of line S is also applied at the far end of the systemconnecting the two halves together through surge resistor R. It shouldbe understood that the total length of section S including the length ofdamping resistance R is onehalf wavelength.

Figs. 4a and 4b illustrate, respectively, the instantaneous currentdistribution by means of dotted lines along the upper and lower halvesof the system of Fig. 4. It will be seen that the two circles 5 and 5'are excited cophasally and therefore aid each other in radiation alongthe horizontal plane. It will be understood, of course, that if desiredany number of these sections may be stacked one above the other, toobtain concentration of energy in the vertical plane.

Fig. 5 shows a modification in which energy is fed from a transmitter T,through a radiationless concentric type of transmission line TL' into aspiral shaped conductor 6, thus obtaining the effect of several circularradiators stacked one above the other to obtain concentration ofradiation in the vertical plane. It is preferred that the turns of thespiral be spaced at least onequarter wavelength apart to minimize mutualinteraction between turns. Since each turn of the spiral is twowavelengths long, the currents in the various turns will be cophasal,and the radiation effects will be cumulative in a plane perpendicular tothe axis of the spiral. The vertical portion of the system of thisfigure is generally located within the spirals of the conductor 6 Fig. 6illustrates an arrangement in which the circular radiator is located atsuch distance above a reflecting earth as to produce substantialconcentration of radiation at an angle a inclined considerably above thehorizontal. The distance above ground should be such that at a distance,the direct ray radiated from the antenna will be cophasal to theindirect ray which is reflected from the ground. For the geometry ofFig. 6, this condition is satisfied when the distance A, B, C is a halfwevelength different from an integer number of wavelengths. It is thuspossible to produce a hollow cone-shaped directive diagram which is verydesirable for some types of work as, for example, beacons for aiding thenavigation of aircraft.

While the current distribution diagrams shown in dotted lines in Figs.1, 4a and 4b suggest a circle having a circumference of two wavelengths,the system may obviously be constructed with parallel conductors ofother lengths, chosen with discretion so as to have the proper radiationcharacteristics. For instance, the influence which the various circleshave upon each other in the stacked antennas shown in Figs. 4 and 5 maybe such as to alter the phase velocity of the conductors, in which casethe diameter will have to be so changed as to make one circumferencehave an electrical length of two wavelengths.

It will be obvious, of course, that the antenna of the invention may beused to radiate vertically polarized waves if the system is orientedsuch that the axis of the circular conductors is horizontal. If thiswere done, then maximum radiation would ordinarily be along a directionperpendicular to the axis of the circular conductor.

What is claimed is:

1. An antenna system for transmitting horizontally polarized wavescomprising a radiating conductor in the form of a circle whose diameteris equal to i where A is the length of the communication wave, saidconductor having uniformly distributed inductance and capacitance andbeing located in the horizontal plane, and means for energizing saidconductor and preventing the formation of standing waves thereon.

2. An antenna system for transmitting horizontally polarized wavescomprising a conductor in the horizontal plane in the form of a circleand having two terminals, another similarly located conductor spacedfrom said first conductor in the vertical plane, means for seriallyconnecting said conductors together for cophasal ener gization thereofincluding a damping impedance coupling together one terminal of oneconductor with the correspondingly located terminal of the otherconductor, and a two-wire substantially radiationless transmission lineone of whose wires is connected to the other terminal of said oneconductor and the other wire of which line is connected through aradiationless loop to the other terminal of said other conductor, thelength of one side of said radiationless loop being a half wavelength.

3. An antenna system fortransmitting horizontally polarized wavescomprising a radiating conductor in the horizontal plane substantiallyin the form of a circle, said conductor having uniformly distributedinductance and capacitance, and means for energizing said conductor andpreventing the formation of standing waves thereon, the length of thecircumference of said circle being substantially an even integer numberof wavelengths, so chosen that the diameter is approximately an oddnumber of half wavelengths, whereby radiation is substantially limitedto the horizontal.

4. An antenna system for transmitting horizontally polarized wavescomprising a radiating conductor in the horizontal plane substantiallyin the form of a circle, said conductor having uniformly distributedinductance and capacitance, and means for energizing said conductor andpreventing the formation of standing waves thereon, the length of thecircumference of said circle being substantially an odd integer numberof wavelengths long, so chosen that the diameter is approximately aneven number of half wavelengths, whereby radiation is substantiallylimited to the horizontal.

5. An antenna system comprising a plurality of substantially parallelradiating loops located substantially along an axis perpendicular to theplanes of said loops, each of said loops having uniformly distributedinductance and capacitance and having a length substantially equal to aninteger times the length of the communication Wave, means for connectingsaid loops in electrically series relation with respect to one another,whereby the energy conductively flows through one loop to the nextadjacent loop, and means for preventing the formation of standing wavesin said loops.

6. An antenna system comprising a plurality of substantially parallelradiating loops located substantially along an axis perpendicular to theplanes of said loops, each of said loops having uniformly distributedinductance and capacitance and having a length substantially equal to aninteger times the length of the communication wave, said radiating loopsbeing spaced apart from one another a distance equal at least toone-quarter the length of the communication wave, means for connectingsaid loops in electrical series relation with respect to one another,whereby the energy conductively flows through one loop to the nextadjacent loop, and means for preventing the formation of standing wavesin said loops.

7. An antenna system in accordance with claim 2, characterized in thisthat said two conductors are spaced approximately one-half wavelengthapart.

8. An antenna system for radiating substantially horizontally polarizedwaves, comprising a plurality of radiating loops located above oneanother and symmetrically with respect to an axis therethrough, each ofsaid loops having uniformly distributed inductance and capacitance andhaving a length substantially equal to an integer times the length ofthe communication wave, means for connecting said loops in electricallyseries relation with respect to one another, whereby the energyconductively. flows through one loop to the next adjacent loop, andmeans for preventing the formation of standing waves in said loops.

HAROLD 0. PETERSON.

